IV medications are usually given via the intravenous line, but can also be given by regular injection, depending on the medication.
These medications have been used for a long period of time for labor and birth. However, timing of these medications are critical because you want there to be a time interval between when these medications are given and when the baby is born to help prevent breathing difficulties at birth.
IV pain medications take effect more quickly that medications like the epidural, but do not remove pain, rather they alter your perception of the pain. They can help promote relaxation or even sleep. Their use can also be combined with epidural anesthesia for the very anxious mother.
Common Medications Used
Pain relief for childbirth has run the gamut over the ages. And the battle is still being fought today. Should a woman have medications or not during birth is not a question that I anticipate an answer for anytime soon. However, some women will choose medication and some will require it for surgical deliveries and complications. Let's just all be thankful that we are no longer buried alive for accepting pain relief in labor as was done in the middle ages.